This is the second article about how to discuss sexual orientation with friends, family and acquaintances. Specifically, the question of sexual orientation being a “choice” or a biologically determined condition is addressed. The vast preponderance of evidence supports the argument that sexual orientation is determined before birth, but much of this evidence is not widely known. Therefore, this article offers various pieces of information from multiple scientific fields that readers may find useful evidence during their own conversations.
Isn’t sexual orientation a choice? Don’t you choose to be gay?
No. Other than the very obvious rhetorical questions that these questions inspire, such as, why would anyone choose to be a second-class citizen when it would be easier to be heterosexual, or, someone who is LGBT chooses to be so as much as you choose to be straight, so why don’t you try choosing to be gay for a year and get back to me about your experiences, there is a vast host of evidence from a variety of fields that cumulatively prove that “choice” has all but nothing to do with orientation.
But before getting into that evidence, let me direct you to Straight: The Surprisingly Short History of Heterosexuality by Hanne Blank. One of the arguments of the book is that modern societies around the world have assumed heterosexuality is the default orientation for humans, but there is no underlying basis for this doxa, a Greek word meaning a common belief or popular opinion. And because of this doxa, there has been no study of heterosexuality. No “gene” identified for heterosexuality, no proof that it is a “normal” orientation. If we start from the point that a particular sexual orientation is “abnormal,” then we risk looking for confirmatory evidence of that belief rather than asking about the drivers of sexual orientation in general.
Now, on to evidence supporting a biological basis for sexual orientation. To be clear, a singular determinant for sexual orientation doesn’t exist. There isn’t a single “gay gene” that if it was simply identified and eliminated in a developing fetus would ensure that only heterosexual babies were born forever and all time. Instead, sexual orientation (straight and gay) is an as yet not understood combination of mostly genetic factors and the early uterine environment that leads to sexual diversity. To be clear, this combination is so common and consistent that the same percent of the populations in China, Australia, Zambia, Fiji, Chile, and Iran are LGBT, whether in 600 BC or AD 2017. The percent is the same, the only difference is how much the society represses homosexuality. If a culture prides itself on stoning to death LGBT individuals, obviously fewer people will self-report as being LGBT than if the culture allows those individuals to marry and have full rights. The consistency of homosexuality among humans, like left-handedness, should be sufficient evidence to indicate that sexual diversity is a naturally occurring feature, but here is more evidence:
Genes have been scientifically proven to influence sexual orientation.
A number of studies of twins have been used to better understand the relationship between genes and sexual orientation. After all, identical twins have identical genes and developed in the same womb, while fraternal twins share only half their genes but developed in the same womb. If sexual orientation was purely genetic, then 100% of identical twins would be exclusively gay or straight…but they’re not. In 2000, a study of 4,901 Australian twins found that 20% of male identical twins and 24% of female identical twins were both gay (interestingly, a study of twins and schizophrenia found that only 50% of identical twins both have the disease, indicating that it, too has factors beyond simply genetics). A 2010 study of all adult twins in Sweden—more than 7,600 twins age 20-47—also found that sexual orientation had a primarily genetic origin, with moderate to large effects from biological (prenatal environment) and social factors (peer groups, sexual experiences, etc.).
To pursue the genetics question further, we must look at chromosomes. In 1993, a study of 114 families with gay sons found that gay men had a statistically larger number of gay male relatives on the maternal side than the paternal side, suggesting the possibility of genetic transmission through the maternal line. DNA linkage analysis was then done on a group of 40 families in which there were two gay brothers, revealing a correlation between male homosexuality and the inheritance of polymorphic markers on the Xq28 chromosome (the subtelomeric region of the long arm of the sex chromosome) in approximately 64 percent of the sibling pairs. The authors of this study concluded they had a statistical confidence level of more than 99 percent that at least one subtype of male sexual orientation is genetically influenced. A later “meta analysis” of all the studies done on chromosomes and sexual orientation indicates that gayness among males has a significant link to this chromosome, but also probably additional genes as well (including probably the pericentromeric region of chromosome 8). However, female sexual orientation does not seem to be linked to Xq28.
In 2015, researchers at the University of California studying 37 sets of identical male twins of which one brother was gay and the other straight and 10 sets of identical twins for which both men were gay found that they could identify sexual orientation with 67% accuracy by monitoring chromosomal changes that affect gene activity and expression (epigenetics). Researchers identified nine areas in the gay twin’s genome where the genes functioned differently. Although their findings faced some criticism, epigenetics is an interesting approach to sexual orientation because it may explain the differences in sexual orientation between identical twins.
More Brothers in a Family Leads to a Statistically Higher Likelihood of a Gay Son.
Okay, so this one doesn’t exactly apply to lesbians, but the more sons in a family, the higher the likelihood that one or more will be gay. In 1997, a study determined that each son has 33% higher odds of being gay than his next oldest brother. Although scientists have yet to figure out the reason behind the correlation, though they speculate it may have to do with the fetal environment, birth order is now one of the most reliable predictors of sexual orientation in men. If sexual orientation was a choice, there would be no mathematical correlation between the birth order of sons in a family and their sexual orientation.
There are Measurable Biological Differences Between Heterosexual and Homosexual Women Probably Related to Androgens in the Womb.
Everyone knows the index-to-ring finger length ratio as a differentiator between lesbians and straight women (yes, it’s a thing), but lesbians are similar to straight men in other ways as well that probably have to do with the release of androgens—male sex hormones such as testosterone—into the womb during fetal development. In another article, for example, we talked about the hypothalamus of lesbians and straight men being similar. In addition, the inner ear and central auditory system in queer women (the first study I’ve seen that reflects both bisexual women and lesbians) are more like those of men than straight women. In another study, researchers compared the eyeblink response following an acoustic stimuli between heterosexual and homosexual men and women. This response is a nonlearned sensorimotor gating mechanism with a robust gender difference (translation: it’s automatic and men and women have different reaction times). As you might have guessed, lesbians have a much more “masculinized” response than straight women.
Animals are gay, too.
According to the University of Oslo, homosexual behavior has been observed in 1,500 animal species. In fact, domestic rams have been used to study homosexuality because approximately 8% are exclusively homosexual while another 18–22% are bisexual. Birds are particularly prone to a fondness of the same sex. Like these lesbian penguins. 10-15% of female western gulls in some populations exhibit same-sex behavior, while 60% of bonobo sexual activity (and bonobos are VERY sexual) is between females. And homosexuality may be the norm for male giraffes: in one study, up to 94% of mountings were between two males, and same-sex activities were conducted 30-75% of the time.
The LGBT community has often focused on emphasizing that sexual orientation is genetically or biologically pre-determined on the assumption that it would be more difficult to justify discrimination if sexual orientation was not a choice, like race or gender. However, it seems also fair to argue that when it comes to civil rights, choice is also a protected category. Religion, after all, is a choice and it is protected extensively. In a free society, even if individuals “chose” to love someone of the same sex, why should that mean those individuals should be treated as lesser?
Oh, and if none of the above arguments work, just mention this: In a study conducted in 2007, women (regardless of sexual orientation) shown sexually explicit images—including nude male and female bodies, heterosexual and homosexual sex, and sex between bonobos—all had increased vaginal blood flow. Except, they had no increased arousal when shown an unaroused, muscular naked man walking along a beach. Yes, women were turned on by monkey sex but not a ripped naked dude. Who’s high and mighty now?